Understanding the Key to Successful Reproduction
Expression of Behavioral Estrus in Dairy Cattle
Dairy
producers have the most control over the service rate in their herds, and
service rate can be improved by increasing estrus detection efficiency. It is
essential that farm personnel accurately assess signs of estrus behavior.
Standing to be mounted by a herdmate is the primary sign of estrus and is the
best indicator of the fertile period. Unfortunately, recent research has shown that
expression of estrus behavior is poor in lactating dairy cows making it
difficult to accurately detect estrus by visual observation alone in a dairy
operation.
Estrus Duration
Older literature and textbooks cite the
duration of estrus behavior in dairy cattle to be about 18 hours (Roberts,
1986). Recent research using radiotelemetric monitoring of estrus behavior,
however, has shown that lactating dairy cows express estrus behavior poorly
compared with dairy heifers (Table 2). Other published reports have estimated
the duration of estrus behavior in lactating dairy cows to be from 7.1 ± 5.4 hours (Dransfield et al., 1998) to
9.5 ± 6.9 hours (Walker et al., 1996).
Although the reason for the reduction in the duration of estrus behavior is not
known, milk production is negatively correlated with duration of estrus
behavior (Harrison et al., 1990). This reduction in estrus duration
significantly impairs estrus detection efficiency in dairy herds.
Table 2. Number of standing
events and duration of estrus (mean ± SD) in Holstein dairy cattle.
|
Item |
Heifers |
Lactating Cows |
|
No. of Animals |
114 |
307 |
|
No. of Standing Events |
16.8 ±
12.8 |
7.2 ±
7.2 |
|
Estrus duration (h) |
11.3 ±
6.9 |
7.3 ±
7.2 |
(Adapted from Nebel et al., 1997)
In
addition, the number of times per day cows are observed, as well as the timing
and location of these observations, profoundly influences estrus detection
rate. Based on the data in Table 2, estrus detection should be conducted at
three to four evenly-spaced 20-minute intervals per day to achieve adequate
results. Certain physiologic factors reduce estrus behavior including: illness,
feet and leg problems, and acyclicity due to nutritional deficiencies or health
problems. Environmental factors such as heat stress, poor footing, or other
environmental stresses may also reduce estrus behavior.